// Copyright (c) 2017 The Ustore Authors.

#ifndef USTORE_HASH_BUZHASH_H_
#define USTORE_HASH_BUZHASH_H_

#include <cstddef>
#include <cstdint>

namespace buzhash {

const uint32_t bytehash[256] = {
    0x12bd9527, 0xf4140cea, 0x987bd6e1, 0x79079850, 0xafbfd539, 0xd350ce0a,
    0x82973931, 0x9fc32b9c, 0x28003b88, 0xc30c13aa, 0x6b678c34, 0x5844ef1d,
    0xaa552c18, 0x4a77d3e8, 0xd1f62ea0, 0x6599417c, 0xfbe30e7a, 0xf9e2d5ee,
    0xa1fca42e, 0x41548969, 0x116d5b59, 0xaeda1e1a, 0xc5191c17, 0x54b9a3cb,
    0x727e492a, 0x5c432f91, 0x31a50bce, 0xc2696af6, 0x217c8020, 0x1262aefc,
    0xace75924, 0x9876a04f, 0xaf300bc2, 0x3ffce3f6, 0xd6680fb5, 0xd0b1ced8,
    0x6651f842, 0x736fadef, 0xbc2d3429, 0xb03d2904, 0x7e634ba4, 0xdfd87d8c,
    0x7988d63a, 0x4be4d933, 0x6a8d0382, 0x9e132d62, 0x3ee9c95f, 0xfec05b97,
    0x6907ad34, 0x8616cfcc, 0xa6aabf24, 0x8ad1c92e, 0x4f2affc0, 0xb87519db,
    0x6576eaf6, 0x15dbe00a, 0x63e1dd82, 0xa36b6a81, 0xeead99b3, 0xbc6a4309,
    0x3478d1a7, 0x2182bcc0, 0xdd50cfce, 0x7cb25580, 0x73075483, 0x503b7f42,
    0x4cd50d63, 0x3f4d94c9, 0x385fcbb7, 0x90daf16c, 0xece10b8e, 0x11c1cb04,
    0x816a899b, 0x69a29d06, 0xfb090b37, 0xf98ef13c, 0x07653435, 0x9f15dc42,
    0x3b43abdf, 0x1334283f, 0x93f3d9af, 0x0cbdfe71, 0xa788a614, 0x4f54d2f0,
    0xd4374fc7, 0x70557ce7, 0xf741fce8, 0xe4b6f661, 0xc630cb98, 0x387a6366,
    0x72f428fd, 0x539009db, 0xc53e3810, 0x1e1a52e5, 0x7d6816b0, 0x040f9b81,
    0x9c99c9fb, 0x9f3af3d2, 0x774d1061, 0xd5c840ea, 0x8e1480fe, 0x6ee4023c,
    0x2fbda535, 0xd88eff7a, 0xd8632a2a, 0x43c4e024, 0x3ef27971, 0xc72866fd,
    0xe35cc630, 0x46d96220, 0x437a8384, 0xe92caf0c, 0x6290a47e, 0xa7bb9238,
    0x0e1000f9, 0x49e76bdc, 0x3acfb4b8, 0x03582b8e, 0x6ea2de4e, 0x2ec1008d,
    0xfcc8df69, 0x91c2fe0a, 0xb471c7d9, 0x778be812, 0x70d29ad1, 0x76411cbf,
    0xc302e81c, 0x4e445194, 0x22e3aa72, 0xb65762e9, 0xa280db05, 0x827aa70e,
    0x4c531a9d, 0x7a60bf4a, 0x8fd95a44, 0x2289aef0, 0xcd50ddc4, 0x639aae69,
    0x5fe85ed6, 0x4ed724ff, 0x00f04f7d, 0x95a5fcb0, 0x88255d15, 0xa603d2c9,
    0xf6956a5b, 0x53ea7f3e, 0xb570f225, 0x2b3be203, 0xa181e40e, 0xc413cdce,
    0xa7cb1ebb, 0xcf258b1f, 0x516eb016, 0xca204586, 0xd1e69894, 0xe85a73d3,
    0x7db2d382, 0xae73b463, 0x3598d643, 0x5087c864, 0xd91f30b6, 0xe1d4d1e7,
    0x73b3b337, 0xceac1233, 0x8edf7845, 0xa69c45c9, 0xdb5db3ab, 0x28cfade8,
    0xebfa49e7, 0xcbc2a659, 0x59cce971, 0x959a01af, 0x8ee9aae7, 0xfb2f01c6,
    0x5a752836, 0x9ed12981, 0x618d05b6, 0x93ec12b3, 0x4590c779, 0xed1317a2,
    0x03fe5835, 0x7ad3c6f7, 0xd4aad5b5, 0x1a995ed7, 0x247bfaa4, 0x69c2c799,
    0x745fa405, 0xc5b9f239, 0xc3d9aebc, 0xa6f60e0b, 0xdf1e91d7, 0xab8e041c,
    0xee3188c6, 0x37377a9e, 0xc0e1a3bf, 0x19a5a9e4, 0x56cb9556, 0xc4d33d3f,
    0xfb1eb03e, 0xf9557057, 0x1be31d37, 0xd1fa65f1, 0xf518d714, 0x570ac722,
    0xf26cf66a, 0x24794d47, 0x8ba2e402, 0x3f5137e6, 0x35be1453, 0x43350478,
    0x9f05ee88, 0x364cf9cf, 0x39a23ee7, 0xa4db8d49, 0xc2ebb3d2, 0xc6fb99d5,
    0xe014dfb0, 0x7156d425, 0xe090a87a, 0x4cc12f78, 0x1b30f503, 0x06694a7a,
    0x68198cd1, 0x2f8345bd, 0x9d79198e, 0xd871943f, 0x22ef6cf4, 0xe81b1c15,
    0x067b61d8, 0xfc4ea4f5, 0xfe6dab57, 0x1bf744ba, 0xa70b6a25, 0xafe6e412,
    0xc6c1a05c, 0x8ffbe3ce, 0xc4270af1, 0xf3f36373, 0xc4507dd8, 0x5e6fd1e2,
    0x58cd9739, 0x47d3c5b5, 0xe1d5a343, 0x3d4dea4a, 0x893d91ae, 0xbb2a5e2a,
    0x0d57b800, 0x652a7cc9, 0x6a68ccfd, 0x62529f0b, 0xec5f36d6, 0x766cceda,
    0x96ca63ef, 0xa0499838, 0xd9030f59, 0x8185f4d2};

class BuzHash {
 public:
  explicit BuzHash(unsigned int n) {
    n_ = n;
    bshiftn_ = n % 32;
    bshiftm_ = 32 - bshiftn_;
    buf_ = new uint8_t[n];
    Reset();
  }
  ~BuzHash() { delete[] buf_; }

  void Reset() {
    state_ = 0;
    bufpos_ = 0;
    overflow_ = false;
  }

  uint32_t Sum32() { return state_; }

  uint32_t HashByte(uint8_t b) {
    if (bufpos_ == n_) {
      overflow_ = true;
      bufpos_ = 0;
    }
    uint32_t state = state_;
    state = (state << 1) | (state >> 31);
    if (overflow_) {
      uint32_t toshift = bytehash[buf_[bufpos_]];
      state ^= (toshift << bshiftn_) | (toshift >> bshiftm_);
    }
    buf_[bufpos_] = b;
    ++bufpos_;
    state ^= bytehash[b];
    state_ = state;
    return state_;
  }

 private:
  uint32_t state_;
  unsigned int n_, bshiftn_, bshiftm_;
  size_t bufpos_;
  uint8_t* buf_;
  bool overflow_;
};
}  // namespace buzhash

#endif  // USTORE_HASH_BUZHASH_H_
